Catalyst and method of preparation



Patented June 25,

:7 PATENT OFFICE CATALYST AND METHOD OF PREPARATION Benjamin WilsonHowk, Wilmington, DeL, as-

signor to E. I. du Pont de Nemours & Company, Wilmington, Del., acorporation of Delaware No Drawing. Application August 23, 1940, SerialNo. 353,936

UNITED STATES lysts. More specifically, it relates to alloy-skeletonmetal sulfide catalysts characterized by high activity and resistance topoisons and corrosion, and to a process for their preparation.

For many years technical progress and commercial development in thefield of catalytic hydrogenation has been largely dependent on the useof the more familiar types of base metal cat- .alyst such as nickel,cobalt, iron, and copper. In general, these catalysts are employedeither in the form of finely divided metals, as oxides, or

as oxidecombinations containing one or more dimcultly reducible oxides,such as chromium oxide, which serve as promoters. Catalysts of I tivityis partly or wholly destroyed by the cor-- rosive action of acids and insome cases by strong alkaiies as well. These disadvantages haveaccordingly operated to restrict the utility of these familiar basemetal catalysts exceptin connection with hydrogenations in which theproblems of poisoningfor corrosion are seldom met.

For the more diiiicuit types of hydrogenations it has been largelynecessary to rely on noble metal catalysts of the platinum sub-grou inorder to accomplish desired hydrogenations for which nickel, cobalt,etc., are unsuited for the reasons set forth above. Although metals ofthis group, particularly platinum and palladium are valuable catalystsfor conducting hydrogenation reactions under adverse conditions, few ifany commercial processes based on their use have been developed onaccount of their relative scarcity and high cost.

It is therefore an object of this invention to provide anewhydrogenation catalyst that is relatively inexpensive, highly active,poison-resistant, and non-corroding. Another object is to provide aprocess for the manufacture of such a catalyst. Still another object isto provide a more effective method for catalytic hydrogenation. Otherobjects will be apparent from the following description of theinvention.

14 Claims. (Cl. 252-2284) These objects are accomplished by treating analloy of an alkali, soluble metal and a metal se-- lected from the groupconsisting of the hydrogenating metals of the 1st,- 6th, and 8th groups5 of the periodic table with an alkali metal sulfide. According to thepreferred embodiments of the invention hydrogenation catalysts areprepared by treating alloys of metal selected from the group consistingof the hydrogenating metals of the 1st, 6th, and 8th groups of theperiodic table and alkali-soluble metals with solutions of alkali metalsulfides and polysulfides at temperatures in excess'of 0., therebypreparing an alloyskeleton metal sulfide catalyst. I

. A hydrogenating metal of the class referred to above, such a iron,cobalt, nickel, copper, tungsten, or molybdenum is alloyed with aluminumpreferably in the proportions of to parts of the former and to 50 partsof the latter, and go the alloy is ground to a fine powder byconventional methods. One hundred parts of the alloy powderis suspendedin 400 parts of boiling water and a solutionof parts .of hydrated sodiumsulfide (NB.2S.9H20) in approximately parts 25 of water added slowlyover a period of i to 1.5

hours. The mixture is boiled with efiicient stirring for an additional 4hours and allowed to settle. The supernatant liquid is separated and thesludge washed once or twice with water by 30 decantation to removesoluble salts. The precipitate is'then taken up in a solution of 100parts of hydrated sodium sulfide and-50 parts of caustic soda in 400parts of water and boiled for 3 to 4 hours to complete the digestion.The product is allowed to settle, the supernatant liquid decanted, andthe sludge washed thoroughly with water until free from alkali, salts,and hydrogen sulfide. The resulting product, which comprises analloy-skeleton metal sulfide cata- 40 lyst supported on alumina, isobtained as a thick aqueous paste ready for use. In some cases,particularly for employment in non-aqueous hydrogenation systems, it maybe desirable to transfer the catalyst to alcohol or some otherappropriate organic liquid.

The following examples set forth certain well defined instances of theapplication of this invention. They are, however, not to be consideredas limitations thereof, since many modifications may be made withoutdeparting from the spirit and scope of this invention.

Example I Two hundred twenty-seven parts of finely 5; groundcobalt-aluminum alloy containing ap- 'suspensibility in liquids. sulfurand alumina indicated a weight ratio of reaction accompanied by theevolution of hydrogen and traces of hydrogen sulfide ensued, and thesuspended alloy was converted to a gray sludge. After boiling for anadditional 4 hours the'mixture'was allowed to settle, the supernatantliquid decanted and the residue washed twice with water to removesoluble salts. The

sludge was then resuspended in a solution con-- taining 1000 parts ofwater, 226 parts of hydrated sodium sulfide, and 113 parts of sodiumhydroxide and boiled during a further period of 4 hours, the water lostby evaporation being replaced from time to time. The catalyst sludge wasthen allowed to settle and was washed with water by decantatlon untilessentially free from alkali, sodium sulfide, andhydrogen sulfide. Theresulting aqueous paste was washed with alcohol and stored underabsolute alcohol. catalyst was characterized by an extremely fine stateof subdivision and a. remarkable ease of Analysis for cobalt,

1.94 parts cobalt, 1.0 part sulfur, and 1.8 parts of alumina. Themolecular ration of cobalt to sulfur was 1:1 and the composition of thecatalyst mixture corresponded to approximately 33 parts of cobaltsulfide supported on 67 parts of hydrated alumina.

Example II A solution of sodium polysulfide was prepared by dissolving533.5 parts of hydrated sodium sulfide (Na2S.9Ha0) in 750 parts of waterand adding 142.6 parts of sulfur with vigorous stiralloy containingabout parts of cobalt and 65 parts of aluminum in 1000 parts of water. Avigorous evolution of gas occurred and the alloy was converted rapidlyto a finely divided black powder. The mixture was boiled four hours.

' table.

The solid was separated from the supernatant liquid by decantation andwashed several times with water to eliminate caustic soda, solublesalts, and hydrogen sulfide. The product was an aqueous paste of finelydivided catalyst comprising essentially cobalt polysulfide on alumina.

Although in the foregoing examples the use of specific alloys andcertain definite procedure for producing corrosion-resistant, sulfactivealloyskeleton hydrogenation catalysts have been referred to, it is to beunderstood that these factors are subject to wide variation within thescope of the invention without departing from the spirit thereof.

In general, the process of the invention is applicable to thepreparation of a new and highly active' class of poison-resistant.non-ccrroding hydrogenation catalysts comprising alloy-skeleton sulfidesand poly-sulfides of metals selected from the group comprising thehydrogenating metals of the 1st, 6th, and 8th groups of the periodicTypical metals of this class are iron, cobait, nickel, copper, silver,tungsten, and molybdenum. According to the preferred embodiments of theinvention, alloys of these metals with apsilicon, which are not onlyreadily attacked by caustic solutions but which ifail to yield sulfidesand polysulfides that are stable in aqueous media.

after completing addition of the sodium polysulfide, and the precipitatewas allowed to settle overnight on a steam bath. The black catalystsludge was washed thoroughly with water until free from soluble saltsand stored as a thin aqueous paste. The product was essentially freefrom alumina, and contained 1.34 moles of sulfur per mole of cobalt.-

Examplc III Two hundred twenty-seven parts of a finely powderedcobalt-aluminum alloy containing about 35 parts of cobalt and 65 partsofaluminum was suspended in 1000 parts of boiling water.

' The mixture was stirred mechanically while add- In general, alloyscontaining as much as 90% or as little as 10% of the hydrogenating metalcomponent and corresponding amounts of the caustic soluble component aresatisfactory for activation. It is particularly convenient, however, toemploy alloys containing between 30 and 50% by weight of hydrogenatingmetal and between 70% and 50% of the soluble metal. Within these limitssuitable alloys are prepared according to any of the conventionalmethods of the prior art, either as binary compositions containing onlyone of each class or component or as multiple compositions containingvarious combinations of metals coming within the scope of the invention.

In the practice of the invention, it is in general preferred to carryout the activation step essentially as described in the examples.However, as i speaking, the activation process comprises treating thealloy with solutions containing sufiicient alkali metal sulfide orpolysulfide to react in equimolecular proportions with. the total amountof the hydrogenating metal contained in the alloy. It is preferred toemploy soluble sulfides or polysulfides of metals such as the alkalimetals which are characterized by a strongly alkaline reaction insolution. The alkali metal sulfides may be employed alone or incombination with caustic alkalies, or a preliminary treatment with thesulfiide may be followed by a treatment with caustic alkali solution tofacilitate a more rapid and complete solution of the alkali-solublecomponent of the alloy. In general, the use of alkali metal sulfidesolutions alone tends to cause the formation of a supported catalyst inwhich the carrier is produced in situ'from the soluble component of thealloy, whereas the use of caustic alkali favors the production ofunsupported oats,

little or no activity.

lysts. Variations in the amount of caustic employed govern to a certainextent the relative proportions of metal sulfide and support in afinishedcatalyst. In accomplishing these results. the mode of bringingtogether the alloy and the sulfide solution may also be variedconsiderably. For example, the alkaline reagent may be added to asuspension of the alloy or the alloy may be added in successive smallportions to the sulfide solution without materially affecting the'quality or properties of the catalyst produced. According to eithervariation it is preferable to operate with solutions at or near theboiling point.

The alloy-skeleton hydrogenating metal sulfide catalysts of theinvention may be conveniently prepared in physical forms adapted foroperation either in batchwise liquid phase or continuous gas phaselwdrogenation processes. In the former instance, the alloysare'preferably reduced mechanically to powders Prior to the activationprocess in order to produce finely subdivided materials that are easilysuspensible in liquids and provide a maximum surface per unit of mass ofcatalyst. Catalysts suitable for operation in gas phase contacthydrogenation processes may be prepared either by briquetting powdered.catalysts or by surface activation of alloy lumps of suitable size. Ingeneral, the alloy-skeleton metalsulflde catalysts of the invention arecharacterized by a remarkable sturdiness, by their outstandingresistance to corrosion bystrong acids and alkalies at elevatedtemperatures, by their indifference to most types of catalyst poisons,and by their high activity and efiiciency in promoting lLvdrogenationreactions under conditions intolerable to the more familiar metal andmetal oxide hydrogenation catalysts.

Alloy-skeleton metal sulfide catalysts are of wide-spread utility in thefield of hydrogenation,

not only because they function smoothly to promote hydrogenationreactions in general, but more especially because of their superioractivity under conditions generally considered unfavorable for catalyticreduction processes. This su periority is clearly evidenced by thefollowing experiments showing various uses for alloy-skeleton cobaltsulfide catalysts, which are typica of those coming within the scope oithe invention.

A mixture comprising 60 parts of cycl'ohexanone, 30 parts of sulfur, and7 parts of alloyskeleton cobalt sulfide catalyst was charged into a highpressure reaction vessel and treated with hydrogen under 1000 to 2000lbs/sq, in. pressure at 150 C. Hydrogen was absorbed smoothly during 8hours. On working up the product according to conventional methods therewas obtained 61 parts of pure cyclohexanethiol, which corresponds to amolecular yield of 86% of theory.

In a similar experiment, the hydrogenation of heptaldehyde and sulfurwith alloy-skeleton cobait polysulfide catalyst gave a high yield ofheptanethiol. These experiments serve to illustrate the sulfactiveproperties of these catalysts. Under similar conditions ordinary nickelor cobalt catalysts are subject to severe poisoning and show Other typesof hydrogenation reactions requiring a sulfactive catalyst and in whichthe catalysts of this invention are particularly useful are thereduction of aliphatic nitriles to th'iols, the cleavage of alkyl andaryl The following experiment demonstrates the resistance ofalloy-skeleton metal sulfide catalysts to the corrosive action of strongacids at elevated temperatures: Fifty parts of nitrobenzene, 70.7 partsof 45% sulfuric acid and 1 part of alloyskeleton cobalt sulfide catalystwere charged into a corrosion-resisting high pressure autoclave andtreated with hydrogen under 500 lbs. pressure at a temperature of 135 to140 C. for a period of 3 hours. on working up the crude hydrogenationproduct there was obtained 10 parts of unreacted nitrobenzene, 19 partsof aniline and 8 parts of p-aminophenol. Conversely, alloy-skeletoncobalt sulfide catalysts promote the hydrogenation of aromatic nitrocompounds such as nitrobenzene smoothly in caustic alkaline media attemperatures below about 115 C. at hydrogen pressures as low as 500lbs/sq. in. From nitrobenzene the products are azobennene, azoxybenzene,and aniline.

Having described. in detail the preferred embodiments of my invention,it is to be understood that I do not limit myself to the specificembodiments thereof except as defined in the following I claims.

I claim: I

1. A process for the manufacture of a highly active, poison-resistant,non-corroding hydrogenation catalyst which comprises treating an alloyof an alkali soluble metal and a metal selected from the groupconsisting of the hydrogenating metals of the 1st, 6th and 8th groups ofthe periodic table with an alkali metal sulfide.

2. A process for' the manufacture of a highly active, poison-resistant,non-corroding hydrogenation catalyst which comprises treating an alloyof an alkali soluble metal and a metal selected from the groupconsisting of the hydrogenating metals of 'the 1st, 6th and 8th groupsof the periodic table in finely divided form with an aqueous solutioncomprising an alkali metal sul-' tide and obtaining alloy-skeleton metalsulfide hydrogenation catalysts.

' soluble metal.

4. The process in accordance with claim 3 characterized in that thealkali metal sulfide is an alkali metal polysulfide.

5. A process for the preparation of a hydrogenation catalyst whichcomprises treating an alloy in finely divided form and in suspension inan aqueous medium containing an alkali metal sulfide and a causticalkali, said reaction being carried out within the temperature range offrom to 100 C. and said alloy consisting of from 10 to 90% of ahydrogenating metal of the 1st, 8th and 8th groups of the periodic tableand 90 to 10% of an alkali soluble metal.

6. A process for the production of a hydrogenation catalyst whichcomprises treating a finely disulfidea to the corresponding thiols, thereduction of sulfurized olefins, the reduction of aromatic sulfo acidsto thiols and hydrocarbons, and the catalytic conversion or certaininorganic salts such as sulfites to a lower valence state.

divided alloy with an aqueous solution of an alkali metal sulfide at atemperature near the boilins point of said solution, said alloycomprising to of a hydrogenating metal of the 1st, 6th and 8th groups ofthe periodic table and '10 to 50% of an alkali soluble metal.

7.111eprocwinaccordancewithcmme characterized in that the hydrogenatingmetal in said alloy is cobalt and the alkali soluble metal is aluminum.

8. A metal sulfide hydrogenation catalyst prepared by a processconsisting of treating an alloy of an alkali soluble metal and a metalselected from the group consisting of the hydrogenating metals of the1st, 6th and 8th groups of the periodic table with an alkali metalsulfide.

9. A metal sulfide hydrogenation catalyst prein finely divided form andin suspension in an aqueous medium containing an alkali metal sulfideand a caustic alkali, said reaction being carried out within thetemperature range of from pared by a process consisting of treating analloy 8. 25 C. to 100 C'., and said alloy consisting of iron 10 to 90%of a hydrogenating metal of the 1st 6th and 8th groups of the periodictable and 91 to 10% of an alkali soluble metal.

10. The catalyst of claim 8 characterized ii that the hydrogenatingmetal is cobalt.

11. The catalyst of claim 8 characterized ii that the alloy is an alloyof cobalt and aluminum 12. The catalyst of claim 8 characterized ii thatthe hydrogenating metal is copper.

13. The catalyst of claim 8 characterized it i that the hydrogenatingmetal is molybdenum.

14. The catalyst of claim 9 characterized i! that the alloy is an alloyof cobalt and aluminum 7 BENJAMINW. HOWK.

